Method of producing hafnium-free &#34;crystal-bar&#34; zirconium from a crude source of zirconium



United States Patent C) METHOD OF PRODUCING HAFNIUM-FREE CRYSTAL-BARZIRCONIUIVI FROM A CRUDE SOURCE OF ZIRCONIUM Ivan Edgar N ewnham, NorthBalwyn, Victoria, Australia, assignor, by mesne assignments, toMallory-Sharon Metals Corporation, a corporation of Delaware N Drawing.Application November 22, 1955 Serial No. 548,547

Claims priority, application Australia- November 22, 1954 4 Claims. (Cl.75-84.4)

This invention relates to an improved method of producing hafnium-freecrystal-bar zirconium from a crude source of zirconium.

This application is a continuation-in-pazt,of pending application SerialNo. 360,320, filed June 8, 1953, now Patent No. 2,791,485, granted May7, 1957.

At the present time, ductile crystal-bar zirconium is prepared fromsponge zirconium by a process involving the formation, and subsequentdecomposition, of zirconium iodide. In the known process, zircon sand isheated with carbon to produce a carbide which is chlorinated to producezirconium chloride. The latter is then reduced by a suitable reducingagent such as magnesium in order to form the sponge zirconium. Zirconsand normally contains impurities such as hafnium, aluminium, iron andvanadium and it is therefore also necessary to include additional stepsin the process in order to remove these impurities. .The normalprocedure for producing pure crystal-bar zirconium is thus of aninvolved nature and this is especially so when the additional steps areincluded to eliminate hafnium and other impurities.

The main objective of this invention is to provide an improved processfor the production of crystal-bar zirconium from a crude zirconiumsource whereby the number of steps in the process is reduced therebyeffecting a considerable reduction in the cost of producing purecrystal-bar zirconium. H

Other objects and advantages of the invention will be apparent from thefollowing description, to those skilled in the art.

In accordance with the invention, a method of producing hafnium-freecrystal-bar zirconium from a crude source of zirconium comprises thesteps of treating the crude source so as to convert the zirconiumtherein into the tetnaiodide form, reducing the tetraiodide of zirconiumto the trihalide form, separating any unreduced iodides of zirconium andother metal impurities from the reduced iodides of zirconium and othermetal impurities, separating the reduced iodide of zirconium from theother reduced iodides by heating the mixture of reduced iodides in orderto disproportionate the reduced iodide of zirconium :and reform thetetraiodide thereof, and finally decomposing the tetraiodide thus formedto produce crystal-bar zirconium. Essentially, therefore, the methodcomprises the conversion of zirconium carbide to zirconium iodide whichis then purified and subsequently decomposed to form crystal-barzirconium.

To enable "a fuller practical appreciation of the invention, we shallnow describe, by way of example, a process in accordance therewithwhereby crystal-bar zirconium is produced from zircon sand containinghafnium, aluminium, titanium, iron and vanadium impurities.

According to this process, crude carbide is first formed by heatingzircon sand with carbon in a graphite resistor furnace or are furnace inknown manner. Conversion of the carbide to iodide is then carried out byheating the carbide in a stream of iodine in known manner to" formzirconium tetraiodide.

The iodides of zirconium and of the metal impurities prepared asdescribed above can be conveniently collected on the cooled coils of aremovable lid or on some other condenser member of a reaction vessel or,alternatively, they may be resublimed on to such a condenser prior tothe next stage in the process. The lid or other condenser membercarrying the zirconium tetraiodide and the iodides of the impurities isthen transferred to another reaction vessel containing powderedzirconium. The vessel is evacuated and heated to 500 C. at whichtemperature the zirconium tetraiodide sublimes and reacts in the bottomof the vessel with the powdered zirconium metal to form the relativelyinvolatile triiodide. At thesame time as the zirconium tetraiodide isreduced, the iodides of iron and vanadium will also be reduced torelatively involatile lower iodide forms and these collect in the bottomof the chamber, together with the" also condenses on the coils and theremainder is reduced to relatively involatile titanium diiodide by thepowdered. zirconium metal in the bottom of the vessel.

The lid or other condenser member on which the unreduced iodides ofhafnium, aluminium and titanium have collected is then replaced by a newcondenser memher and once again the vessel is evacuated and heated to350 C. During this second heating stage, the zir-j conium triiodidedisprop'ortionates in accordance with and pure zirconium tetraiodidewill be condensed on the" coils of the condenser which are kept cooldurin'g the heating of the vessel in this stage of the process. Theresidue in the vessel consists of the reduced iodides of titanium, ironand vanadium together with a mixture of zirconium and zirconiumdiiodide, and is used as the reducing agent for the next batch of impureiodide in place of the powdered zirconium referred to above as thereducing agent used at the commencement of the process.

The lid or other condenser on which the pure zirconium tetraiodide hasbeen collected is then removed from the vessel and the iodide obtainedtherefrom is passed over a heated zirconium wire in known manner inorder to decompose the iodide and form crystal-bar zirconium.

The process in accordance with the invention thus enables hafnium-freecrystal-bar zirconium to be produced from a crude zirconium source bythe direct conversion of carbide to iodide and thereby eliminatesseveral steps from the known procedure. The reduction step in theprocess in which the higher iodides are reduced to lower iodides enableshafnium, aluminium and other metals, the iodides of which are notreduced by zirconium metal or other reducing agent used in the process,to be separated while the subsequent heating step in the process inwhich the reduced iodide of zirconium disproportionates, enables otherimpurities such as iron and vanadium, the iodides of which are reducedwhen the reduction of zirconium tetraiodide to zirconium triiodide takesplace, to be removed. Titanium, and other metals which form loweriodides with disproportionation temperatures close to that of zirconiumtriiodide, can be partly removed on the coils as volatile iodides andpartly Patented May 5,v 19 59 collected at the bottom of 'e vessel ascomparatively involatile lower iodides. It is possible to retain anyreduced titanium iodide in thejinvolatile residue by making use ofthefact that, although zirconium triiodide is disprbpor'tionated attemperatures triiodide does not commence to disproportionate until thetemperature exceeds 350 C.

It will thus be apparent that the process in accordance with the instantinvention will be instrumental in effecting a substantial advance in theart and will bring about a considerable reduction in the cost ofproducing hafnium-free crystal-bar zirconium.

I claim:'

' 1. A method ofproducing hafnium-free crystal-bar: zirconium from acrude source of zirconium comprising the steps of treating the crudesource so as to convert the zirconium therein into the tetraiodide form,reducing the tetraiodide of zirconium to the trih'alide form, separatingunreduced iodides of zirconium and other unreduced iodides of metalimpurities from the reduced iodides of zirconium and other reducediodides of metal impurities, separating the reduced iodide of zirconumfrom the other reduced iodides by heating the mixture of reduced iodidesin order to disproportionate the reduced iodide of zirconium and reformthe tetraiodide thereof, and finally decomposing the tetraiodide thusformed to produce hafnium-free crystal-bar zirconium.

2.. A method of producing hafnium-free crystal-bar. zirconium from acrude source of zirconium containing hafnium, aluminium, titanium, ironand vanadium impurities comprising the steps of treating the crudesource so' as to convert the zirconium therein into the tetra- 3. Amethod of producing hafnium-free crystal-bar zirconium from zircon sandcontaining hafnium, alu' minium, titanium, iron and vanadium impuritiescomprising the steps of heating the sand with carbon to produce crudecarbide,

heating the crude carbide in a stream of above 310 C., titanium" s 4,iodine to convert the zirconium into the tetrahalide form, heating thetetrahalide in vacuo at a temperature of about 500 C. in the presence ofa reducing agent to convert the zirconium to the trihalide form andreduce the iron and vanadium and a proportion of the titanium torelatively involatile lower iodide forms, separating unreduced iodidesof zirconium, aluminium, hafnium and titanium from the reduced iodidesof zirconium, iron, vanadium and titanium, heating the reduced iodidesin vacuo at a temperature of about 350 C. to disproportionate thereduced iodide of zirconium and reform the tetraiodide thereof,condensing the reformed tetraiodide and separating it from the residuecomprising the reduced iodides of zirconium, iron, vanadium andtitanium, and finally decomposing the reformed zirconium tetraiodide to.form hafnium-free crystal-bar zirconium- 4. A method of producinghafnium-free crystal-bar" zirconium from a crude source of zirconiumcomprising the steps of treating the crude source so as to convert thezirconium therein into the tetraiodide form, reducing the tetraiodide ofzirconium to the trihalide form by means of a reducing agent, separatingunreduced iodides of zirconium andother unreduced iodides of metalimpurities which are not reduced to lower halide forms by the reducingagent from the reduced ,h'alides of zirconium and other reduced iodidesof metal impurities which are reduced to lower halide forms by thereducing agent, heating the reduced iodides to disproportionate thereduced iodide of zirconium and reform the tetraiodide thereof,separating the reformed tetraiodide of zirconium from the reducedhalides of zirconium and the metal impurities which have been reduced tolower halide forms by the reducing agent, and finally decomposing thetetraiodide thus formed to produce hafnium-free crystal-bar zirconium.

References Cited in the file of this patent UNITED STATES PATENTS2,670,270 Jordan Feb. 23, 1954 2,714,564 Loonam Aug. 2, 1955 FOREIGNPATENTS 660,397 Great Britain Nov. 7, 1951 698,235 Great Britain Oct.14, 1953 722,901 Great Britain Feb. 2, 1955 OTHER REFERENCES Steel, vol.127, No. 4, July 24, 1950, pages 63-65.

1. A METHOD OF PRODUCING HAFNIM-FREE "CRYSTAL-BAR" ZIRCONIUM FROM ACRUDE SOURCE OF ZIRCONIUM COMPRISING THE STEPS OF TREATING THE CRUDESOURCE SO AS TO CONVERT THE ZIRCONIUM THEREIN INTO THE TETRAIODIDE FORM,SEPATHE TETRAIODIDE OF ZIRCONIUM TO THE TRIHALIDE FORM, SEPARABLE RATINGUNREDUCED IODIDES OF ZIRCONIUM AND OTHER UNREDUCED IODIDES OF METALIMPURITIES FROM THE REDUCED IODIDES OF ZIRCONIUM AND OTHER REDUCEDIODIDES OF METAL IMPURITIES, SEPARATING THE REDUCED IODIDES OF ZIRCONUMFROM THE OTHER REDUCED IODIDES BY HEATING THE MIXTURE OF REDUCED IOFIDESIN ORDER TO DISPORPORTIONATE THE REDUCED IODIDE OF ZIRCONIUM AND REFORMTHE TETRAIODIDE THEREOF, AND FINALLY DECOMPOSING THE TETRAIODIDE THUSFORMED TO PRODUCE HAFNIUM-FREE "CRYSTAL-BAR" ZIRCONIUM.